Overhead doors are commonly used in loading docks, garages, factories, and other settings where large door openings are periodically closed off. Conventional overhead doors typically include a plurality of rectangular door panels pivotally connected along their upper and/or lower edges. Rollers or other guide members can extend outwardly from each side of the door panels, and can be received in corresponding guide channels of door tracks that extend upwardly along each side of the door opening. Some door tracks, often referred to as “vertical lift” door tracks, extend vertically, or at least generally vertically, above the door opening so that the door is retracted into a generally vertical position when opened. Other door tracks, often referred to as “standard lift” or “high lift” door tracks, turn horizontally and extend away from the door opening so that at least a portion of the door is retracted into a generally horizontal position when opened.
Overhead doors can be manually or automatically operated, and typically include a counterbalance mechanism that partially offsets the weight of the door. Automatic overhead doors can include an arm that extends between the door and an operator track parallel to upper portions of the door tracks. A motor and a looped belt or chain can be used to control movement of the arm along the operator track. In this way, movement of the door can be regulated to a slow and steady speed. Some automatic overhead doors can be converted into manual overhead doors, e.g., by disengaging the arm from the belt or chain. Other overhead doors are capable of automatic or manual operation only. Manual overhead doors typically are configured such that an operator can manually lift and lower the door using a handle, a rope, or some other similar mechanism.
In contrast to automatic overhead doors, manual overhead doors are typically more prone to harsh operation leading to more significant wear on components. For example, manual overhead doors may be improperly opened or closed with excessive force. Some overhead door assemblies include an upper bumper that stops the door from moving beyond a fully open position. These upper bumpers can fail due to the impact or mechanical shock associated with forcefully opening the door. Similarly, other portions of overhead door assemblies can fail due to impact or mechanical shock associated with forcefully closing the door, e.g., shock that occurs when the door hits the floor beneath the door opening. Furthermore, in some cases, overhead doors can recoil from fully open and/or fully closed positions after forceful impact, leaving the doors in less desirable partially open or partially closed positions. Overhead doors can also drift down from open positions due to factors other than recoil (e.g., poorly adjusted counterbalance mechanisms).
One conventional approach to reducing mechanical shock and the associated component wear that result from harsh operation of overhead doors includes incorporating raised features (e.g., bumps) in the door tracks. When used with doors including retractable (e.g., spring-loaded) guide members, the raised features can force the guide members to partially retract, thereby absorbing energy and slowing movement of the doors. Retractable guide members are often used in overhead doors to allow the doors to release from the door tracks in response to accidental impact against the door panels. Most overhead doors, however, include non-retractable guide members (e.g., fixed rollers). In some cases, raised features in door tracks are not compatible with overhead doors including non-retractable guide members. Furthermore, repeatedly forcing retractable guide members over raised features can wear down or otherwise damage the guide members over time. Accordingly, there is a need for further innovation in the field of overhead doors, such as new approaches to reducing the negative effects of harsh operation, reducing recoil, reducing drift, and/or addressing other problems stated or not stated herein.